Creatures in the attic

We live on the outskirts of Brussels. There is a family of creatures living in my attic, more specifically under the eaves – I had a glimpse of one the other night and I think it’s a marmotte (or possibly a fouine). I know where they are coming in, but for obvious reasons I don’t want to block it (I don’t want to trap them inside). I am pretty sure that mama gave birth recently. She goes out at night time - making a terrific amount of noise – I believe she brings food back for the babies. We have called a pest control guy who will come next week. However, I don’t have a tremendous amount of confidence in him. He proposes to put poison down. I really don't want dead furry corpses in the attic, particularly as the part where I believe they are nesting is inaccessible to humans. I am also concerned about the cruelty aspect and am wondering if there is some other way to get them to move house! Is there some environment service or wildlife protection board around Brussels that can advise? Thanks all.